By mounting. First you need a mount-point, i.e. a directory under which
you can access your floppy. You can chose an arbitrary name, I use /df0
through /df3 (and /pc0 to /pc3 respectively) because I'm used to these
names from AmigaOS.

Like under AmigaOS with CrossDOS, drive 0 is a single physical unit. Note
that this is different from Linux/i386. You can verify this by reading
Documentation/devices.txt of the kernel source. The nodes fd* above are
remnants of a Intel configuration; only the major/minor numbers count, not
the assigned name!

Now, MS-DOS drive 0 can be accessed by /dev/fd0 as well as
/dev/pc0. If you want /dev/fd0 to be an Amiga drive, link it to
/dev/df0 instead. Of course, this are just examples from my
configuration. You can choose other names if you like.

After having mount-point and device-node, you can mount your floppy.

For an AmigaOS disk in drive 0:

mount -t affs /dev/df0 /df0
ls /df0
...
umount /df0

For a MS-DOS disk in drive 1:

mount -t msdos /dev/pc1 /pc1
ls /pc0
...
umount /pc0

Warnings:

Only mount if floppy already in drive and

you must not remove the floppy before umount'ing it!

You can also put this into your /etc/fstab file. Mine looks like this:

You can use the "mtools" package to access MS-DOS disks without the
need of mount/umount. The mtools-3.6.tar.gz package compiled
without any problems out of the box for me. The nodes /dev/fd0 and
/dev/fd1 are used to access the MS-DOS drives. If you followed my
descriptions above it is not necessary to edit mtools.conf (in /etc or
/usr/local/etc)

Hhm. Good question. There are some binaries in
bin/system/floppy at ftp.uni-erlangen.de.
Unfortunately for me, fdformat dies with a segmentation fault
and amifdformat-formatted disks can't be mounted using
affs. Any suggestions are welcome!